Huge dynamic Stark shifts of atomic energy levels in xenon induced by high-intensity laser light have
been mesured by a new method based upon multiphoton ionization by a tunable femtosecond laser source.
Stark-induced multiphoton resonances appear as identifiable structures in the photoelectron energy spectra1. The
change in the structures positions, when the photon energy is tuned, is directly related to the energy change of
the atomic levels as a function of intensity. Shifts of the order of the electron-volt have thus been measured in
xenon and found to vary linearly with intensity.